Apple chief executive Steve Jobs and Microsoft Chairman Bill Gates have committed to a rare joint appearance at the fifth anniversary of the The Wall Street Journal's 'D: All Things Digital' conference later this year. The two men, both seminal figures in the development of the personal computer, will jointly discuss the history and future of the digital revolution in an unrehearsed, unscripted, onstage conversation on May 30 with D co-producers Walt Mossberg and Kara Swisher.